Imagine RUclips being like this, informative, factual, low-key, friendly, educating .... it makes he happy to have found this video and a bit sad that there is also so much garbage around. Thank you so much sir!
@@FAMUCHOLLYYou do realize everything on a computer is either data or "software algorithm", right? The fact you can watch this video or read my comment is made possible via a software algorithm.
Sturgeon's law is strong in the Internet in general, RUclips is sadly no different in this way. But like you said at least we have videos/channels like this!
@@RockBrentwood nothing wrong with wanting immediate answers, but that's not what they were getting at. They were emphasizing the chill and friendly vibe, which is to say the human element.
Thanks for the great, well-rounded explanation. I must insist however, that 1) Kermit the Frog is often considered a 'star'. 2) He sings about being green. and 3) He appears green. (At least to me, that is.) (When he doesn't appear grey, that is.)
It's like trying to play a tiny piano with oven mitts on. You can hit the low note, you can hit the high note, but if you try to play Middle C you hit all the notes.
@@paulfellows5411 Hm, yes I see the distinction. I'll torture the analogy: Playing a tiny piano by slapping a rattle snake across the keys with the left hand while banging out a beat on a tambourine. The _Hiss Rattle Snake Shake._
I love that the answer comes down to the fact that eyes are weird and black body radiation doesn't come in sharp peaks. Excellent video, certainly earned my subscription.
22:44 oh my goodness!! This is why I’ve always felt like if I needed to focus on something in the dark, I’d stare off to the side and look at the thing with my peripheral because it appears to be brighter that way. Thank youu!
If I remember properly, our Sun actually sends out most of its visible light in the green spectrum, but like you said the yellows and reds balance it to a yellow. The sun being primarily green seems like it works well with chlorophyll being green, since chlorophyll uses light to make sugars. Until you remember that being a color means that’s the color you *reflect* so leaves actually use every color *except* green to make sugar!
Yes indeed, some people have mentioned the point about plants being green and got it the wrong way round. You have it right. Plants are green because they can’t use it. Red light has energy sufficient to liberate one electron. Blue light liberates two. But green would be one-and-a-half and that’s not helpful : a plant would get an electron and the rest dumped as stray energy which might not do it any good! Of course some living things have different systems and so have red or black leaves when they have evolved ways to use the light differently.
@ oh wow I didn’t know that second part! So chlorophyll is green not just by an accident of evolution, but it really is more effective. If I remember properly, all plants use chlorophyll and non-green leaves just mean a different chemical is more prevalent in the leaf. So they are still reflecting the green but a different color dominates. Same idea to how deciduous leaves change color in the fall as they replace their chlorophyll with winterizing chemicals, just all year round. I’m not sure though, you’ve already taught me one thing in this thread!
@@52flyingbicycles Don't forget that that there's nothing saying that plants had to use chlorophyll. In fact, from what I understand, many experts believe the current green colour is exactly an accident of evolution. The hypothesis is that early light-harvesting archea were purple because they absorbed the abundant green light, perhaps using retinal. Chloroplasts evolving in deeper water underneath just did what they could with the remaining light, and only later came to dominate. It's only a theory AFAIK, but it seems a pretty neat one to me.
I greatly enjoy how the end answer to the question is breif, but it can only be breif by building on a large foundation of other information that initally looks unrelated. This is the hallmark of a good teacher.
I was taking off in Atlanta during winter inversion. Looking at the false sunrise, I saw the most brilliant green flash of light from the sun for just a second before going its usual yellow-white color.
When I was a kid I made this dumb "parody" (more like ripoff/sequel) to Star Wars with cats, called "Cat Wars" and to make my stupidly overpowered anthro aliens even more extra special I made them orbit a green star. This video just reminded me about that
Yes, but I define the colour as the perceptual appearance that the brain gives. Becuase to do it based purely on the peak wavelength would mean there would be no white stars :-)
Yes that’s why plants are green on earth!! There’s so much of it that they can afford to reflect it. Thereoticallyn plants in exoplanets orbiting other types of stars would emit light respective of their parent star, like around a dim red dwarf for example plants would probably be dark red or even black bc of the dim light and need to absorb as much of it as they can where as a plant of a planet orbiting a superior blue star (in the Goldilocks zone of course) would be bluish or purplish. There are a few RUclipsr docs that touch of this thereoticall life concept, Melodysheep comes to mind
Colour is what we perceive in the brain, not the wavelength : consider this Very very hot stars peak in the UV but we see them as blue . And really cool stars peak in the infrared, we see them as dim red.
Thanks. If you are interested in this sort of stuff and want more, try “Does the Sun have a Dark Heart” or “Quark Stars and Strangelets” which has been very popular.
VERY nicely done, Professor Fellows. Excellent, well thought out setup and a payoff that was short, sweet, and straight to the point. I knew Sol was green, but now I also understand why. THANKS!
Peaks in the green. But mixed with a little blue and a lot of red … so looks pale yellowish white. If it were hotter (6500C rather than 5800C ) it would be an equal mix making white due to a bit more blue.
Thanks. There are 150 other videos on a wide range of astronomy and other related topics which I made, but for some reason this one seems to be going a bit viral, while the rest lie unwatched :-)
I’m so glad I found you channel! I love astronomy and physics and your presentation here grabbed my attention and held onto it for the entire video. Can’t wait to watch more of your stuff ❤
Thank you. If you are interested there are lots more that I have published. For some reason this one has had a hundred times the number of views, but I’m sure you can find the others just as interesting
@@paulfellows5411 The reason this got so many views is because you asked an interesting/intriguing question in the title. I had a quick look at the other videos and not sure I would understand from the title
Another way to put it. When the peak emission is in the green, our eye's range of spectral response admits too much of that red and blue to permit the green hue to be perceptible. There is a lack of sufficient color purity, and the result is essentially colorless. But we can enjoy the sensation of green when two stars are in angular proximity and each has a particular temperature/spectral type. An A star seen next to a K star can have the former exhibit a sensible green, which is brought out by contrast with the orange conpanion. An isolated star having even the 'ideal' spectral curve, such as alpha Librae mentioned by another commenter, is quite difficult to see as other than essentially without hue. Perhaps under certain conditions of ambient lighting or sky glow color might a greenish tint be perceived.
@@glennledrew8347 indeed, our eyes / brain combination is quite complicated in terms of the perception of colours. In the simple case of a single star vs a black background it is how I have described it. As you say the spectral response of our eye has quite broad and overlapping peaks, especially for red and green ( even in non-colourblind people) But if you put two different colours next to each other , the brain can do weird things - it has a tendency to recalibrate the average of the perception towards the normal daylight balance that it expects, and that messes with what is perceived. A number of optical illusions depend on this.
I wonder if the mythical green solar ray (the title of a Jules Verne story but apparently a genuine although rarely observed atmospheric phenomenon) is not something in this vein.
@@troppoandante That phenomenon you refer to is called the green flash. It is not commonly seen, and generally requires a very low horizon, with the sea itself being ideal. Consider sunset. When the last visible part of the Sun's upper limb is just about to disappear, the spectral dispersion by the atmosphere induces a slight color separation, rather like a weak prism differentially refracting light passing through a slit. If the atmospheric transparency is amenable to passing sufficient green light (usuall it's blue being most dimmed and red least), that final bit of the Sun can for a moment appear a noticeable green. The state of atmospheric steadiness (or turbulence) can play a role too. Again, this is a pretty uncommon sight, most folk never having witnessed it in their entire lives. Of course, specifically looking for it increases the odds of catching the right atmospheric conditions. 😉
Green doesn’t happen until you have red and blue wavelengths. So it makes sense that the stars are not green, unless as the comment above stated, there are two stars.
I didn’t know I had that question until I say your video! Thank you so much for explaining it all so distinctly and well. I don’t know much about the natural sciences but despite that I was able to understand because of how you explained and illustrated everything. :)
Thanks. There are about 150 others, but for some weird reason this one has gone viral, while the rest lie almost ignored! I did them all during lockdown, one a week each Saturday as live presentations on zoom while our meetings were not possible!
Dear sir, i can't thank you enough for the set of informative, awe-inducing lessons you've produced over the years. I can safely say your hiatus from RUclips of the past two years had been my sorest gripe with the internet as a whole, now finally relieved!
Thank you. There was a lot going on in my personal life but things are back to normal now thankfully I hope to add more, and your encouragement is most welcome
Thanks for explaining it, and for giving me the tools to explain for myself why there also aren't any violet stars. It's a bit sad for me, green being my favorite color. Would like to see a green star. But I suppose I shouldn't complain at how beautiful the stellar rainbow we do have already is
This was a fantastic video. Thank you Mr. Fellows for your excellent work. Subscribed to you Sir, I look forward to exploring what you have for videos!! TYVM!
I am very pleasantly surprised by the algorithm for suggesting me this video and your channel, it seems like you actual took the effort to have a “conversation” with yourself and think what a less knowledgeable but curious viewer would wonder about during the video, and then filled that gap, amazing 🙏, i am subscribed.
This was pretty great and I learnt a lot specially about the eyes so thanks for that, although I thought that it might be illuminating to add a small section explaining why stars don’t just emit one specific wavelength of light, since that is the underlying reason why the green doesn’t appear in the first place, but otherwise no complaints, great work explaining simply and with multiple disciplines :)
Thanks Diving into the Planck/Bolztman statistical mechanics that explains the black-body spectrum is something I could try to cover in another video. Thanks for the suggestion
Most comprehensive, thank you. I recall, though, reading (possibly in a Poul Anderson story) that objects that are undergoing temperature increase have their peak wavelengths narrowed, isolating that color. In the story that was the explanation of the greenish star; it was leaving the main sequence and getting hotter. Whether this effect can actually work on something as large as a sun is... debatable, I guess.
@ lol..👍 good on you Nate! I ve 40 years in engineering.., studied all kinds of interests.., but I’ve been lazy on that.. , I just accepted stars are red- yellow - blue.. I love your coupling the wonder of Eukaryotic development.. with.. & within that of the universe 👍 cheers from 🇳🇿
I was just going about my day, expecting it to be a normal one at that. Then a video title catches my attention and my brows furrow. The kind of furrow that makes your entire face seem like it is about to collapse. "How have I never wondered this?" Well, you don't know what you don't know, I guess.
Thank you. It’s hit 50000 views. Most of my other talks (there are 150 of them) have had ~100 views. I’m sure people would like them but RUclips’s algorithm is a law unto itself:-) I made over a hundred during covid. One every Saturday as a live zoom cast, and recorded them. Enjoy
Stellar atmosphere composition mostly results in absorbsion lines which only slightly affect color. The atmosphere of a planet can significantly affect what color a star appears to be. eg. red/orange hue near the horizon
Glad you enjoyed it! I have lots of other videos uploaded on here, but for some reason this one has had more views in a week that all the rest put together over a period of years….
Thanks. I really didn’t expect this one to rocket up the rankings like it has. It’s just one of about 150 of my talks that I do at the institute of astronomy in Cambridge for the public and most of them get recorded, posted and viewed less that 500 times… this one 85 thousand and counting. The pittance of revenue from it will all go into funding the Cambridge Young Astronomers kids program, but every little helps!
So if we had less red color receptor “cones” or no red “cones” at all, we would be able to see green stars? But I guess that would make the lower energy stars less visible or maybe invisible. If we had additional color receptor “cones”, like other animals do, maybe between the green and the blue, we should be able to see all the green stars that appear yellow. Hell, we could have “violet cones” and see even more stars colors. It is all in our biology and brain!
Yea, no red cones would make yellow stars look green, white stars look cyan etc Some people are colour-blind in this sort of way…. There is also some evidence that, becuase the colour receptor genes are on the X chromosome, females can have two different versions of green, and that they might get expressed at the same time. Men only have one of each. Perhaps this explains a lot about clothes shopping :-)
A pretty cool way i found to visualize this is by creating an image in photoshop with multiple layers of different colors. If you set the layer blend mode to additive, you see this effect take place. I was not able to get this to replicate the bright blue effect, but ill just blame that on my display not supporting uv light
Yeah I might have to try something like that. The slides are mostly from a short talk to the public open night crowd at the university observatory which I gave about 20 years back, when it was cloudy and we couldn’t stargaze! I dug it out, dusted it off and added a few extras to make this video, and wham 50,000 people have watched it in a week! Most of the other videos have a few hundred views or less. Thank you for the suggestion!
I propose, that when we have the ability in the far future, we should make a mostly clear Dyson sphere around a white or yellow star that blocks or absorbs red and orange light, making the star appear green. That energy could be then used. Then we could also make one that blocks out orange yellow and green to make a purple star as well. At least that would make them easy to pick out at night! 😜
At a company designing aircraft instrumentation they explained that they were experimenting with lights to simulate movement in the pilot's peripheral vision, because that senses faster. Sitting at my computer I can testify to that, I sense birds, people and cars and look to the right at the window. The company were using yellow light because peripheral vision is more sensitive in that region. And they would be advised by universities.
It would have been fun with the ending if you then had shown a green sunset. It happens very rarely due to some atmospheric conditions, and can be rather pretty. Try to make a Google search to see it.
The colours that the eye-brain combination constructs can be mapped onto a cube with R,G and B axes. Brown turns out to be a dark yellow-orange : a mix of a low intensity red and green, but with more red than green. Typically 50% red and 25% green with zero blue will look brown. Your screen makes it appear I that way by lighting up a the red and green sub pixels in the right proportions. But you don’t get proper stars that appear brown, because as in the video, you tend to find that once something is hot enough to produce green light there tends to be more green than red. For brown you need it the other way around and also fairly dim. JavaScript for web pages recommends in hex 9B4D00 So 9B red, 4D green and zero blue So in decimal that’s 155, 77, 0 out of 255 max for each colour.
The peak of the energy spectrum is indeed in the green as people seem to want to point out 😊 But this does not determine the overall perceived colour because that comes from the eye/brain perception of the integration sum of the energy across the received wavebands. So the mix of red orange and yellow adds to the green and prevents one seeing green.
Very good presentation. Another way of putting it is that even though the Sun peaks in green, our visual system is optimized to work in sunlight (and similar conditions), and compensates for the uninteresting (for survival) abundance of green. Only the way objects alter the ambient light has any real use in a natural setting - in order to see what it is - so our brains interpret sunlight as white.* Indeed our brain is so good it it, that it'll switch in a moment the colour balance from sunlight (greenish white) to incandescent (typically red) to fluorescent (usually very green) to shade on a sunny day (very blue) and we see *all* of it as just plain white unless we have another light source to compare it to. (if anybody wants to test it, look at a piece of paper under the different lighting conditions - and for reference take photos of the paper as well, with a camera with a fixed colour balance) *) The "white" sunlight is the sum of all the ambient light from the Sun, both the direct light, and the light scattered in the atmosphere. So on a Sunny day it's the sum of the yellowish Sun and the bluish sky, near sunset it's the sum of the reddish Sun and the sky of many colours, and on an overcast day it's the sum of all the frerquencies scattered through the consequently grey clouds.
True, but this is not just about the Sun, it’s a fact about all stars - as you say a combination of the curve of the black body radiation spectrum and the way our eyes work with our Brain, and the latter does indeed play tricks! One oddity is that because our cones have red and Green response curves (normally) which overlap the brain is dealing with and unscrambling the overlapping channels so , depending on which wavelengths of red and green you chose exactly, the brain has to sort out Channel 1 = 3x red - green Channel 2 = 3x green-red This leads to all sorts of fun with optical illusions. I feel another video coming on 😮
Interesting that the physical size of stars are inversely proportionate to their mass! Your star color/size graphic looks funny to me. I expected the blue star to be smaller, and the "Red Giant" to be larger.😂
For ordinary stars low mass means small, higher mass bigger size. But giant-stars are not ordinary. They have gone beyond fusion of hydrogen to helium in their cores. The physics is a bit complicated for these. Maybe I should make another video…. So “red giants” are enourmous, but very low density.
The sun isn’t green though. It might have peak power in the green, but to appear green that would have to massively dominate the other colours, and it doesn’t.
@paulfellows5411 Haha it's a reference. In the webcomic "Homestuck" there is a Green Sun that represents a star bigger than the universe itself. Its purely fictional, but the title and topic of the video was ironic as a fan of the story. Thanks for the informative video and reply however 👍💕
Very interesting information. Do you think that this distribution of blue and white stars could explain the Fermi paradox? There are more blue/white stars in the arms where we live, and we know it's not really feasible for life to form around these stars. They live too short of a life for anything to develop. The galactic core is also assumed to be relatively inhospitable to life due to it's deadly amounts of radiation and regular novae going off. So maybe in a few billion years, when the arms are more populated with yellow/orange stars, there will be a lot more life out here and therefore easier for us to detect.
Great questions. The prevalence of giant stars in one’s galactic neighbourhood is a bad thing due to their tendency to explode. The Sun orbits the galaxy in about 230 Million years and the probably encounters the spiral arms several times per orbit. This may explain some of the extinction events that we are aware of in earth history
![The Insane Science of Neutron Stars [4K]](http://i.ytimg.com/vi/qX6h72IyKSo/mqdefault.jpg)
Imagine RUclips being like this, informative, factual, low-key, friendly, educating .... it makes he happy to have found this video and a bit sad that there is also so much garbage around. Thank you so much sir!
@RockBrentwood, your reply shows EXACTLY why humans should NEVER rely on software algorithms for providing serious information...😒
@@FAMUCHOLLYYou do realize everything on a computer is either data or "software algorithm", right? The fact you can watch this video or read my comment is made possible via a software algorithm.
Wow, thank you!
Sturgeon's law is strong in the Internet in general, RUclips is sadly no different in this way. But like you said at least we have videos/channels like this!
@@RockBrentwood nothing wrong with wanting immediate answers, but that's not what they were getting at. They were emphasizing the chill and friendly vibe, which is to say the human element.
Thanks for the great, well-rounded explanation. I must insist however, that 1) Kermit the Frog is often considered a 'star'. 2) He sings about being green. and 3) He appears green. (At least to me, that is.) (When he doesn't appear grey, that is.)
@@msmith2646 you make an excellent point. An aspect I had not considered. I now know what my final slide should have been :-)
Don't forget the Hulk.
Is Dark Kermit a black hole?
I would add that he also does perform a type of fusion even, bringing the kids of the world together.
I thought he was kinda yellowish?
EDIT: TIL I learned about colorblindess 😮
Watching a lecture that you choose to watch is so much more enjoyable than one you're forced to attend
Right on!
The trick is to get the students interested in the topic.
To show them it has utility.
I genuinely appreciated the mini biology section, learned way more than I expected haha
Cool, interesting how it’s all connected isn’t it
It's like trying to play a tiny piano with oven mitts on. You can hit the low note, you can hit the high note, but if you try to play Middle C you hit all the notes.
@@Clone42 well, it’s more that to get to your chosen key you have to walk in from the left across the keyboard playing all the lower notes too ,
@@paulfellows5411 Hm, yes I see the distinction. I'll torture the analogy: Playing a tiny piano by slapping a rattle snake across the keys with the left hand while banging out a beat on a tambourine. The _Hiss Rattle Snake Shake._
No... if you had oven mitts on it wouldn't matter what note you're trying to hit. You would hit multiple notes regardless
I guess it's like playing a piano, but with a giant plank of wood that you have to move in from the left.
@@jackthurman2642have you visited reality yet?
I love that the answer comes down to the fact that eyes are weird and black body radiation doesn't come in sharp peaks. Excellent video, certainly earned my subscription.
Spot on!
22:44 oh my goodness!! This is why I’ve always felt like if I needed to focus on something in the dark, I’d stare off to the side and look at the thing with my peripheral because it appears to be brighter that way. Thank youu!
If I remember properly, our Sun actually sends out most of its visible light in the green spectrum, but like you said the yellows and reds balance it to a yellow.
The sun being primarily green seems like it works well with chlorophyll being green, since chlorophyll uses light to make sugars. Until you remember that being a color means that’s the color you *reflect* so leaves actually use every color *except* green to make sugar!
Yes indeed, some people have mentioned the point about plants being green and got it the wrong way round. You have it right. Plants are green because they can’t use it.
Red light has energy sufficient to liberate one electron. Blue light liberates two. But green would be one-and-a-half and that’s not helpful : a plant would get an electron and the rest dumped as stray energy which might not do it any good!
Of course some living things have different systems and so have red or black leaves when they have evolved ways to use the light differently.
@ oh wow I didn’t know that second part! So chlorophyll is green not just by an accident of evolution, but it really is more effective.
If I remember properly, all plants use chlorophyll and non-green leaves just mean a different chemical is more prevalent in the leaf. So they are still reflecting the green but a different color dominates. Same idea to how deciduous leaves change color in the fall as they replace their chlorophyll with winterizing chemicals, just all year round. I’m not sure though, you’ve already taught me one thing in this thread!
@@52flyingbicycles Don't forget that that there's nothing saying that plants had to use chlorophyll. In fact, from what I understand, many experts believe the current green colour is exactly an accident of evolution. The hypothesis is that early light-harvesting archea were purple because they absorbed the abundant green light, perhaps using retinal. Chloroplasts evolving in deeper water underneath just did what they could with the remaining light, and only later came to dominate. It's only a theory AFAIK, but it seems a pretty neat one to me.
I greatly enjoy how the end answer to the question is breif, but it can only be breif by building on a large foundation of other information that initally looks unrelated. This is the hallmark of a good teacher.
Exactly what I was trying for :-)
a wonderful explanation of black body radiation physiologically without ever calling it "back body radiation".
Spot on :-)
I was taking off in Atlanta during winter inversion. Looking at the false sunrise, I saw the most brilliant green flash of light from the sun for just a second before going its usual yellow-white color.
Yup I’ve seen it do the green flash , refraction in the atmosphere where the image is split
When I was a kid I made this dumb "parody" (more like ripoff/sequel) to Star Wars with cats, called "Cat Wars" and to make my stupidly overpowered anthro aliens even more extra special I made them orbit a green star. This video just reminded me about that
Should be a movie like Space Balls.
Do it! I'd love to see that.
Absolutely amazing! I've always wondered about this myself and the explanation at the end hit me like a freight truck
Likewise:-)
Very well explained. Excellent visually too.
Glad you liked it!
If you define a stars color as the wavelength where its energy peaks, then our stars is, indeed, green.
Yes, but I define the colour as the perceptual appearance that the brain gives. Becuase to do it based purely on the peak wavelength would mean there would be no white stars :-)
@ yes but the other is wayyyy funnier. 😀
Yes that’s why plants are green on earth!! There’s so much of it that they can afford to reflect it.
Thereoticallyn plants in exoplanets orbiting other types of stars would emit light respective of their parent star, like around a dim red dwarf for example plants would probably be dark red or even black bc of the dim light and need to absorb as much of it as they can where as a plant of a planet orbiting a superior blue star (in the Goldilocks zone of course) would be bluish or purplish.
There are a few RUclipsr docs that touch of this thereoticall life concept, Melodysheep comes to mind
The sun is our star. We live on a planet.
Colour is what we perceive in the brain, not the wavelength : consider this
Very very hot stars peak in the UV but we see them as blue .
And really cool stars peak in the infrared, we see them as dim red.
Exactly what we need more of on RUclips! Smart, Informative people (not A.I.) sharing knowledge. Thank you, Sir.
Best explanation I have seen, thanks!
EXCELLENT lecture. I've always found the hallmark of a good teacher is explaining complex things in simple ways.
Thanks. If you are interested in this sort of stuff and want more, try “Does the Sun have a Dark Heart” or “Quark Stars and Strangelets” which has been very popular.
VERY nicely done, Professor Fellows. Excellent, well thought out setup and a payoff that was short, sweet, and straight to the point.
I knew Sol was green, but now I also understand why. THANKS!
Peaks in the green. But mixed with a little blue and a lot of red … so looks pale yellowish white.
If it were hotter (6500C rather than 5800C ) it would be an equal mix making white due to a bit more blue.
I love being recommended super ineresting videos like this. Thanks for sharing this lecture, I learned a lot.
Glad you enjoyed it!
Thank you! I'll recommend this video to my students. Nice explanation.
Thanks. There are 150 other videos on a wide range of astronomy and other related topics which I made, but for some reason this one seems to be going a bit viral, while the rest lie unwatched :-)
Fascinating! Thanks for posting.
Paul, thank you. Astronomy deserves long form lectures so no detail goes missed, there are so many, and you respect the intelligence of your audience.
Very kind, thanks. Try “quark stars and strangelets” you might like that too!
I’m so glad I found you channel! I love astronomy and physics and your presentation here grabbed my attention and held onto it for the entire video. Can’t wait to watch more of your stuff ❤
Super interesting and well put, thanks!
Brilliant film composition.
Thank you. If you are interested there are lots more that I have published. For some reason this one has had a hundred times the number of views, but I’m sure you can find the others just as interesting
@@paulfellows5411 The reason this got so many views is because you asked an interesting/intriguing question in the title. I had a quick look at the other videos and not sure I would understand from the title
Superb presentation 👏
Big like for this comprehensible explanation! 👍
Another way to put it. When the peak emission is in the green, our eye's range of spectral response admits too much of that red and blue to permit the green hue to be perceptible. There is a lack of sufficient color purity, and the result is essentially colorless.
But we can enjoy the sensation of green when two stars are in angular proximity and each has a particular temperature/spectral type. An A star seen next to a K star can have the former exhibit a sensible green, which is brought out by contrast with the orange conpanion.
An isolated star having even the 'ideal' spectral curve, such as alpha Librae mentioned by another commenter, is quite difficult to see as other than essentially without hue. Perhaps under certain conditions of ambient lighting or sky glow color might a greenish tint be perceived.
@@glennledrew8347 indeed, our eyes / brain combination is quite complicated in terms of the perception of colours.
In the simple case of a single star vs a black background it is how I have described it. As you say the spectral response of our eye has quite broad and overlapping peaks, especially for red and green ( even in non-colourblind people)
But if you put two different colours next to each other , the brain can do weird things - it has a tendency to recalibrate the average of the perception towards the normal daylight balance that it expects, and that messes with what is perceived. A number of optical illusions depend on this.
I wonder if the mythical green solar ray (the title of a Jules Verne story but apparently a genuine although rarely observed atmospheric phenomenon) is not something in this vein.
@@troppoandante That phenomenon you refer to is called the green flash. It is not commonly seen, and generally requires a very low horizon, with the sea itself being ideal. Consider sunset. When the last visible part of the Sun's upper limb is just about to disappear, the spectral dispersion by the atmosphere induces a slight color separation, rather like a weak prism differentially refracting light passing through a slit. If the atmospheric transparency is amenable to passing sufficient green light (usuall it's blue being most dimmed and red least), that final bit of the Sun can for a moment appear a noticeable green. The state of atmospheric steadiness (or turbulence) can play a role too.
Again, this is a pretty uncommon sight, most folk never having witnessed it in their entire lives. Of course, specifically looking for it increases the odds of catching the right atmospheric conditions. 😉
@@glennledrew8347 I’ve seen the green flash , and photographed it too. It’s very quick.
Green doesn’t happen until you have red and blue wavelengths.
So it makes sense that the stars are not green, unless as the comment above stated, there are two stars.
That explained it ,thanks, always wondered why.
I didn’t know I had that question until I say your video! Thank you so much for explaining it all so distinctly and well. I don’t know much about the natural sciences but despite that I was able to understand because of how you explained and illustrated everything. :)
Yes, master. I enjoyed your video very much. Thanks again for your amazing easy-to-understand explanation.
the graph on 8:42 remembers me of csgo ak 47 recoil pattern. Thank you so much for the lecture
This has been the first explanation that has made sense to me. I really appreciate your replies in the comments breaking it down further too
Thanks
This was such a great presentation
@@berttorpson2592 thank you.
I’ve got about 150 others - the perfect cure for insomnia:-)
What an absolutely legendary video. Thank you, sir.
Glad you enjoyed it!
Great explanation and great video! I have asked myself this question before but I never thought the answer would be simple.
I did enjoy that, thank you Paul!
Thanks. There are about 150 others, but for some weird reason this one has gone viral, while the rest lie almost ignored! I did them all during lockdown, one a week each Saturday as live presentations on zoom while our meetings were not possible!
Great explanation! Loved the video.
I learned something today. Great content.
Glad to hear it!
Plenty more if you liked that one, about 150 to choose from ;-)
Dear sir, i can't thank you enough for the set of informative, awe-inducing lessons you've produced over the years.
I can safely say your hiatus from RUclips of the past two years had been my sorest gripe with the internet as a whole, now finally relieved!
Thank you. There was a lot going on in my personal life but things are back to normal now thankfully
I hope to add more, and your encouragement is most welcome
Not a question I’ve ever asked but I’m glad I watched anyways!
Thanks for explaining it, and for giving me the tools to explain for myself why there also aren't any violet stars.
It's a bit sad for me, green being my favorite color. Would like to see a green star. But I suppose I shouldn't complain at how beautiful the stellar rainbow we do have already is
For Short answer 23:30
Thats was a great explanation
Thanks, nice to have the effort appreciated.
Thank you so much. Very informative and well presented. Now I’ll definitely remember why there are no green starts!
Outstanding in both presentation and explanation! Thank you very much!
You're very welcome!
well done, thank you
I expected the astronomy lesson. I didn't expect the biology lesson! 10/10
Thanks - it’s the linkage across the sciences that I enjoy talking about most!
Try my “snowball Earth” video :-)
Very informative thanks!
Glad it was helpful!
Excellent video! Concise, well presented, and engaging. Thanks!
Epic homestuck reference
Fantastic video and well taught. Thank you. I found it really interesting
If you liked it, there are 150 others out there. I made them during lockdown to keep from going nuts. Some say it didn’t work
@@paulfellows5411 I'm planning on it, your channel is a gold mine.
Best and most understandable explanation. I assume that if you filter out the orange and red light we would then actually see green star as green?
Thanks, and yes you have it right.
I’ve got about 150 o the videos up on here, but for some reason this one has gone viral! Do check out the others!
This was a fantastic video. Thank you Mr. Fellows for your excellent work. Subscribed to you Sir, I look forward to exploring what you have for videos!! TYVM!
I was happy to see the phrase "wiggling about" on the diagram of star temperature and colors.
Fantastic video, easy to follow and interesting enough that you won't get bored. Very well presented and nice to look at, too.
Thank you!
That was really interesting, thank you sir
Glad you enjoyed it… about 150 of my others to enjoy
really like how this video was put together. makes me feel like i'm back in school. :) thanks for making such a cool informative video!
You’re very welcome
I am very pleasantly surprised by the algorithm for suggesting me this video and your channel, it seems like you actual took the effort to have a “conversation” with yourself and think what a less knowledgeable but curious viewer would wonder about during the video, and then filled that gap, amazing 🙏, i am subscribed.
Welcome aboard! That’s exactly what I’m aiming for!
"Cool things glow in infrared", puts picture of himself in infrared. Absolute chad move.
This was pretty great and I learnt a lot specially about the eyes so thanks for that, although I thought that it might be illuminating to add a small section explaining why stars don’t just emit one specific wavelength of light, since that is the underlying reason why the green doesn’t appear in the first place, but otherwise no complaints, great work explaining simply and with multiple disciplines :)
Thanks
Diving into the Planck/Bolztman statistical mechanics that explains the black-body spectrum is something I could try to cover in another video. Thanks for the suggestion
This was brilliant, thank you!
Great to hear. This one has reached 50,000 people. Most of my vids have just sat at a few hundred, ignored. It’s all a mystery!
Most comprehensive, thank you. I recall, though, reading (possibly in a Poul Anderson story) that objects that are undergoing temperature increase have their peak wavelengths narrowed, isolating that color. In the story that was the explanation of the greenish star; it was leaving the main sequence and getting hotter. Whether this effect can actually work on something as large as a sun is... debatable, I guess.
nicely done
Thanks
This was pretty cool.
Great video. Has me wondering what daylight would look like here on Earth if we had a different color star.
Excellent 🙏🙏🙏🙏
Thank you. This question puzzled me for years until I eventually figured it out.
@
lol..👍 good on you Nate!
I ve 40 years in engineering.., studied all kinds of interests.., but I’ve been lazy on that.. , I just accepted stars are red- yellow - blue..
I love your coupling the wonder of Eukaryotic development.. with.. & within that of the universe 👍 cheers from 🇳🇿
I was just going about my day, expecting it to be a normal one at that. Then a video title catches my attention and my brows furrow. The kind of furrow that makes your entire face seem like it is about to collapse. "How have I never wondered this?"
Well, you don't know what you don't know, I guess.
Exactly… this puzzled me for years until I figured out the answer :-)
Marvellous voice good sir
I thought Top Gear was changing subjects.
pretty neat explanation, thx
The algorithm did great work recommending this!
Thank you. It’s hit 50000 views. Most of my other talks (there are 150 of them) have had ~100 views. I’m sure people would like them but RUclips’s algorithm is a law unto itself:-)
I made over a hundred during covid. One every Saturday as a live zoom cast, and recorded them.
Enjoy
Does the chemical composition of the star have any affect on its color, or is it simply heat? I know most gasses are invisible, and stars are plasma?
Stellar atmosphere composition mostly results in absorbsion lines which only slightly affect color. The atmosphere of a planet can significantly affect what color a star appears to be. eg. red/orange hue near the horizon
The vast majority is just due to the temperature, the absorption/emmission lines make a tiny difference
Nice explanation.
Glad you enjoyed it! I have lots of other videos uploaded on here, but for some reason this one has had more views in a week that all the rest put together over a period of years….
@@paulfellows5411 Where are the other videos located?
Nice video hit the homepage for a lot of people
Thanks. I really didn’t expect this one to rocket up the rankings like it has.
It’s just one of about 150 of my talks that I do at the institute of astronomy in Cambridge for the public and most of them get recorded, posted and viewed less that 500 times… this one 85 thousand and counting.
The pittance of revenue from it will all go into funding the Cambridge Young Astronomers kids program, but every little helps!
So if we had less red color receptor “cones” or no red “cones” at all, we would be able to see green stars?
But I guess that would make the lower energy stars less visible or maybe invisible.
If we had additional color receptor “cones”, like other animals do, maybe between the green and the blue, we should be able to see all the green stars that appear yellow.
Hell, we could have “violet cones” and see even more stars colors.
It is all in our biology and brain!
Yea, no red cones would make yellow stars look green, white stars look cyan etc
Some people are colour-blind in this sort of way….
There is also some evidence that, becuase the colour receptor genes are on the X chromosome, females can have two different versions of green, and that they might get expressed at the same time. Men only have one of each. Perhaps this explains a lot about clothes shopping :-)
@ Very interesting! Thank you professor.
Cool!! I bet this phenom has a relationship with the appearance of our planet's light harvesters
A pretty cool way i found to visualize this is by creating an image in photoshop with multiple layers of different colors. If you set the layer blend mode to additive, you see this effect take place. I was not able to get this to replicate the bright blue effect, but ill just blame that on my display not supporting uv light
Yeah I might have to try something like that. The slides are mostly from a short talk to the public open night crowd at the university observatory which I gave about 20 years back, when it was cloudy and we couldn’t stargaze! I dug it out, dusted it off and added a few extras to make this video, and wham 50,000 people have watched it in a week! Most of the other videos have a few hundred views or less.
Thank you for the suggestion!
First class video!
Thanks! Glad you enjoyed it
I propose, that when we have the ability in the far future, we should make a mostly clear Dyson sphere around a white or yellow star that blocks or absorbs red and orange light, making the star appear green. That energy could be then used. Then we could also make one that blocks out orange yellow and green to make a purple star as well. At least that would make them easy to pick out at night! 😜
I wonder what happened to the guy that walked into the dangerous dark forest with a floodlight and a siren? I'm sure he was fine.
@@SleepyHarryZzz we do use bells to avoid bears 🤔
Thank you, Cambridge gentleman sir.
At a company designing aircraft instrumentation they explained that they were experimenting with lights to simulate movement in the pilot's peripheral vision, because that senses faster. Sitting at my computer I can testify to that, I sense birds, people and cars and look to the right at the window. The company were using yellow light because peripheral vision is more sensitive in that region. And they would be advised by universities.
It would have been fun with the ending if you then had shown a green sunset.
It happens very rarely due to some atmospheric conditions, and can be rather pretty.
Try to make a Google search to see it.
As has been pointed out, I should have ended with Kermit, well known for being a green star!
If you were to look at a white star with glasses that reflected/filtered red light, would it appear green?
No, it would be ( White minus red ) which would be Cyan ( ie Green plus blue) because white = red + green + blue
wow theres probably over a hundred stars in that image.
thanks for sharing the talk
Glad you enjoyed it. I have about 150 other talks on here if you are truely bored :-)
The diagram at 21:00 - is there an explanation for the lack of blue cones upper left of center?
They look poisson-disc like, otherwise.
Not sure I understand the question sorry
16:04 the colour map also prompts the question, where does the colour brown come from?
The colours that the eye-brain combination constructs can be mapped onto a cube with R,G and B axes. Brown turns out to be a dark yellow-orange : a mix of a low intensity red and green, but with more red than green. Typically 50% red and 25% green with zero blue will look brown.
Your screen makes it appear I that way by lighting up a the red and green sub pixels in the right proportions.
But you don’t get proper stars that appear brown, because as in the video, you tend to find that once something is hot enough to produce green light there tends to be more green than red. For brown you need it the other way around and also fairly dim.
JavaScript for web pages recommends in hex 9B4D00
So 9B red, 4D green and zero blue
So in decimal that’s 155, 77, 0 out of 255 max for each colour.
I'd love to investigate the spectra of things that appear brown, but I have no clue how to start.
@ sounds like you like Brown notes…
Brown is a darker shade of orange. Brown doesn't 'exist'.
Brown is orange with *context*
I have told people this. Our sun is white, but the dominant wavelength is green. Even color temperature is green with a wide bandwidth.
The peak of the energy spectrum is indeed in the green as people seem to want to point out 😊
But this does not determine the overall perceived colour because that comes from the eye/brain perception of the integration sum of the energy across the received wavebands. So the mix of red orange and yellow adds to the green and prevents one seeing green.
What colour are plants generally?
23:24 You're Welcome :)
Congrats in the new job, Clarkson
Thank you!
sick video twin
Very good presentation. Also no such colour as pink. Its just light minus green, greens a very interesting colour.
Yes, you are right
Better defined as magenta.
there was also a video showing there is no orange, it's in fact brown when viewed more clinically
This is what the internet was made for!
Thank you!
Very good presentation.
Another way of putting it is that even though the Sun peaks in green, our visual system is optimized to work in sunlight (and similar conditions), and compensates for the uninteresting (for survival) abundance of green. Only the way objects alter the ambient light has any real use in a natural setting - in order to see what it is - so our brains interpret sunlight as white.*
Indeed our brain is so good it it, that it'll switch in a moment the colour balance from sunlight (greenish white) to incandescent (typically red) to fluorescent (usually very green) to shade on a sunny day (very blue) and we see *all* of it as just plain white unless we have another light source to compare it to. (if anybody wants to test it, look at a piece of paper under the different lighting conditions - and for reference take photos of the paper as well, with a camera with a fixed colour balance)
*) The "white" sunlight is the sum of all the ambient light from the Sun, both the direct light, and the light scattered in the atmosphere. So on a Sunny day it's the sum of the yellowish Sun and the bluish sky, near sunset it's the sum of the reddish Sun and the sky of many colours, and on an overcast day it's the sum of all the frerquencies scattered through the consequently grey clouds.
True, but this is not just about the Sun, it’s a fact about all stars - as you say a combination of the curve of the black body radiation spectrum and the way our eyes work with our Brain, and the latter does indeed play tricks!
One oddity is that because our cones have red and Green response curves (normally) which overlap the brain is dealing with and unscrambling the overlapping channels so , depending on which wavelengths of red and green you chose exactly, the brain has to sort out
Channel 1 = 3x red - green
Channel 2 = 3x green-red
This leads to all sorts of fun with optical illusions.
I feel another video coming on 😮
Interesting that the physical size of stars are inversely proportionate to their mass!
Your star color/size graphic looks funny to me. I expected the blue star to be smaller, and the "Red Giant" to be larger.😂
For ordinary stars low mass means small, higher mass bigger size.
But giant-stars are not ordinary. They have gone beyond fusion of hydrogen to helium in their cores. The physics is a bit complicated for these. Maybe I should make another video…. So “red giants” are enourmous, but very low density.
Homestuck, having a Green Sun: Hold my space time continuum.
The sun isn’t green though. It might have peak power in the green, but to appear green that would have to massively dominate the other colours, and it doesn’t.
@paulfellows5411 Haha it's a reference. In the webcomic "Homestuck" there is a Green Sun that represents a star bigger than the universe itself. Its purely fictional, but the title and topic of the video was ironic as a fan of the story. Thanks for the informative video and reply however 👍💕
@ too deep for me :-)
Loved this,definitely earned a sub. Looking forward to more lectures
@@Perichron welcome on board :-)
There are about 150 of my talks on here and more to come!
Very interesting information. Do you think that this distribution of blue and white stars could explain the Fermi paradox? There are more blue/white stars in the arms where we live, and we know it's not really feasible for life to form around these stars. They live too short of a life for anything to develop. The galactic core is also assumed to be relatively inhospitable to life due to it's deadly amounts of radiation and regular novae going off. So maybe in a few billion years, when the arms are more populated with yellow/orange stars, there will be a lot more life out here and therefore easier for us to detect.
Great questions. The prevalence of giant stars in one’s galactic neighbourhood is a bad thing due to their tendency to explode.
The Sun orbits the galaxy in about 230 Million years and the probably encounters the spiral arms several times per orbit. This may explain some of the extinction events that we are aware of in earth history
Have you ever seen the color green in the sunset? Most of the rest of the rainbow is there somewhere, but it's hard to find green.
I have seen the green flash at sunset. Yes